1. Field of the Invention
This invention relates to a circuit breaker within an insulating housing, and more particularly, it pertains to a magnetic circuit air gap adapted, at low lever overcurrents, to avoid premature tripping of the circuit breaker.
2. Description of the Prior Art
For some applications, it is desirable to provide a circuit breaker having a variable magnetic circuit air gap to obtain a time delay effect. For example, for a motor circuit protection it is desirable that a circuit breaker includes a magnetic circuit adapted to enable a delay of the trip function at low level overcurrent conditions so that motor starting transient currents do not prematurely trip the circuit breaker.
Heretofore, manual means for selectively adjusting the overcurrent valve for tripping a circuit breaker have been provided. However, such means have not been completely suitable for all applications because a motor starting current typically includes an inrush current pulse that can be up to twice the value of normal starting current of the motor. Since magnetic tripping devices are usually designed to trip or operate according to starting current values, the inrush pulse can be quite disruptive to the function of the tripping device.